glennhl

Sorry, wrong. A bigger front bar makes the car push more (understeer). A bigger rear bar makes the car oversteer.

shopdog

Nope. In a turn, a car's body rolls, transferring weight to the outside tire and unloading the inside tire. This reduces front end grip until at the limit the outside tire breaks away and you wind up going nose first into the weeds. This is understeer. A stiffer front antisway bar transfers weight from the outer tire to the inner tire, generating more total grip in the front and allowing the car to stay in the turn against a higher centrifugal force without the nose heading for the weeds. If the car was neutrally balanced to begin, the rear will now break loose first, and you have oversteer. So a stiffer front bar makes the car tend to oversteer.

The same holds true in reverse for the rear bar. If the car starts out neutral, stiffening the rear bar transfers weight to the unloaded inner rear tire allowing the rear to stick better, so the front breaks loose first, and you have understeer. So stiffening the rear bar makes the car tend to understeer.

Stiffening the bar at one end of the car makes the other end of the car looser (relatively speaking).

matuszynski

hmmmmm, someone is wrong on this one.

MitchAlsup

Consider an infinitely stiff front sway bar. A bar so stiff that both front tire always remain at the same ride height wrt the chassis.

Here once the chassis develops any roll (like say while cornering) the inside front wheel will come up off the paved surface! Thereby, the inside front tire cannot possibly be delivering any traction to the front of the car while turning.

Thereby, stiffer front sway bars induce understeer.

jschindler

You seem to be alone in your thinking. I've been reading about suspensions as long as you have, and everything I have ever read contradicts your stance.

matuszynski

wouldn't be the first time that is for sure.

Jeffvette

http://www.springmountainmotorsports.com

From the video, if you can't follow the line out of there, I can only imagine what it's like in the esses.

glennhl

Mitch, you have a lot more patience than I do, plus you are excellent at explaining things. I like taking things to the 'limit' in order to explain things, like you did using the analogy of an infinitely stiff front sway bar. Very well done! I've used the logic of taking it to the 'limit' in order to make my wife understand things and it works. It will be interesting if it works on Shopdog or not?

C6400hp

I've never said this before and probably never will again but, YOU ARE WRONG. Please forgive me Shopdog you must be having a brain fart today
http://www.circletrack.com/techartic...n_brake_setup/
http://www.racelinecentral.com/RacingSetupGuide.html
http://www.240edge.com/performance/tuning-bars.html
http://www.whiteline.com.au/default..../faqelse01.htm

shopdog

So, if we're to believe your theory, the softer the antisway bars, the better a car would corner. At the limit, no bars at all would corner best. Hmmm, wonder why Chevy puts bigger bars on its "sportier" packages then. Are they trying to limit the cornering ability of the Z51 and Z06 to less than that of the base suspension?

The answer is no they are not, and the reason why is that you're thinking about the problem the wrong way. What you're missing is that the antisway bars tie together the unsprung weight of the car, but not the sprung weight of the car. The total lateral friction force of an unloaded tire is less than that of one which is loaded. F=kW/A So if the sprung weight (the vast majority of the weight of the car) rolls away from the inner tire, it loses traction. What the antisway bar does is transfer some of that weight back to the inner, allowing it to grip better. The stiffer the bar, the greater the weight transfer. In the limit case with the bar being infinitely stiff, half of the sprung weight will be transferred to the inner tire. This is ideal because the inner and the outer tires will now have equal grip, and the car will corner as hard as possible before the tires break loose and let it slide.

Of course the ride would be horrible on a bumpy surface in that case because if one wheel encounters a bump, the other would feel it equally, thus defeating the purpose of independent suspension. So they don't make the antisway bars infinitely stiff. But at least on a smooth surface, infinitely stiff bars would be ideal, and on rougher than perfect surfaces, you still want to make the bars as stiff as is compatible with keeping the car from bouncing into the air over bumps.

'06 Quicksilver Z06

He is wrong more often than some here like to admit.

I'd hardly be asking for his "forgiveness." Wrong is wrong. He should be retracting his original statement and asking us to excuse his error, as opposed to anyone here apologizing to him for their being right.

davekp78

What you are saying is true if you had infinately hard springs. But in a real car a stiffer sway bar wants to LIFT the inside wheel, due to body roll, thus reducing the total grip.
Get a copy of "Tune to Win" by Caroll Smith.

mlongo99

While it doesn't completely invalidate your argument, this statement is not true. Think back to your first dynamics class and draw a free body diagram of the situation. The centripital acceleration from going around the curve creates a lateral force. This force creates a moment on the car that wants to induce body roll. With the infinitely stiff bar preventing body roll (we'll neglect the roll that tire flex will allow) there must be an equal and opposite moment acted upon the car to prevent any roll motion from occuring. The only other forces acting are coming from the ground through the tires' contact patches. These are the forces of the ground counteracting the car's weight. In order for these to provide a net moment on the car, the left vs right rides must be unequal. Therefore, even if no body roll is occurring around the corner, there is still an uneven weight distribution between the left and right side.

Blocktrdr

All this is wrong. First, in the C5 where the cars had the same suspension geometry, the Z06 had a different front bar. The rears were the same. This helped counter the oversteer that would come from the extra HP. Also, the sway bars have to fit in with the rest of the suspension. When they stiffen the springs and shocks they stiffen the sway bars to match.

If a car is turning right the body rolls left. The spring compresses. The sway bar wants to follow it up. On the right side the suspension extends. The sway bar tries to counter this and transfers load away from the tire, not to it. All else being equal, the no sway bar would offer the most grip. The problem is that at a certain point the car rolls enough that the center of gravity raises. The other issue is that the further the car rolls the longer it takes so transient response suffers.

Thus sway bars should be at the happy medium wher the car generates the most grip while losing the least CG and maintaining the best transient response.

jschindler

Well spoken. I too have an awful lot of respect for Shopdog, and I appreciate that you are going out of your way to try to show the respect he deserves even when dissagreeing with him.

Blocktrdr

As to the original poster, Corvettes, like pretty much all street cars, understeer. If the car oversteers unintentionally you are doing something wrong. Your video is too short to tell, but if I had to guess I'd bet you have corner entry understeer that is turning into corner exit oversteer. In other words, in the early part of the corner you are turning the wheel too far. the fronts are scrubbing. as the car scrubs speed passing mid corner the fronts get better grip. Now you are getting on the power but your steering wheel is turned too far. The rears loose some of their lateral ability because they are now trying to accelerate the car as well. That's when the rear steps out. No matter what, you are not hitting "track out" on your video. You need to unwind the wheel more coming out of the turn. The best thing you could do is spend your money on some instruction. It will make way more difference than any suspension parts you are going to buy.

ronsc1985

On IRS cars such as a Vette stiffening the front bar will lessen under steer. What may be causing some of the confusion in this thread is that on some live axle cars the opposite is true ie. over steer increases. This is not true on all live axle cars but it does happen on some depending on where you are starting from.

BTW all street cars by design under steer as this is a much safer condition for the average driver. It's probably a safer condition for most race cars by not always the fastest way around the course depending on what the course is.

jschindler

I dissagree with that as well. Makes no difference whether it is IRS or solid axle. Bigger bars on front increase understeer, bigger on back increases oversteer.

'06 Quicksilver Z06

Once again, I agree with JSchindler.

There are already reports here of people going to the larger Z06 rear sway bar and keeping the existing front Z51 sway bar and ending up with more oversteer.

Its part of why I won't put a Z06 rear sway bar on my own car. I have experience enough oversteer as it is when I autocross the car.

I thought it was common knowledge that bigger front bars increase push/understeer, and bigger rear bars increase oversteer.

ronsc1985

You are free to disagree however the facts are that in a car which was designed to roll a great deal in the corners a stiffer bar prevents excessive positive camber from occurring on the front tires in a turn. This effect is sometimes stronger than the extra weight transfer and the result is less understeer.